Loop stitch shuttle for sewing machines



June 3, I969 YASUKATA EGUCHI 3,447,498

LQOP STITCH SHUTTLE FOR SEWING MACHINES Sheet Filed June 8, l96'7 June 3, 1969 YASUKATA seucr-u 3,447,493

LOOP STITCH SHUTTLE FOR SEWING MACHINES Filed June a, 1967 Sheet 2 of 4 Q Q 3 fimgugm h I lNV-ENTOR kQyWLA at "M "m", BY, I

June 1969 YASUKATA EGUCHI 3,447,498

LOOP STITCH SHUTTLE FOR SEWING MACHINES Filed June a, 1967 Sheet of 4 F/G' 6E F/G16'F F/G. 6G F/G 6H if I 71m LJ/ v June 3, 1969 YASUKATA EGUCHI 3,447,498

LOOP STITCH SHUTTLE FOR SEWING MACHINES Filed June 8, i967 Sheet 4 of 4 INYENTOR.

United States Patent 3,447,498 LOOP STITCH SHUTTLE FOR SEWING MACHINES Yasukata Eguchi, Tokyo, Japan, assignor to Janome Sewing Machine Co., Ltd., Tokyo, Japan Filed June 8, 1967, Ser. No. 644,696 Claims priority, application Japan, June 9, 1966,

41/ 36,801; July 11, 1966, 41/44,791

Int. Cl. D05b 1/06, J/

U.S. Cl. 112-197 13 Claims ABSTRACT OF THE DISCLOSURE Background of the invention Loop stitches are used for basting material in such a manner that the row of stitches can be easily ripped. Loop stitches are used for temporarily attaching labels and for sewing shrinkable and expansible material such as tricot and jersey cloth. The operation for making a loop stitch on a sewing machine is quite dilferent from the formation of standard stitches since the period for maintaining the thread loop large and open is different and the loop stitch is formed of a single thread. It is known to use for loop stitching a special oscillating shuttle in which the caught thread loop is held whereupon the catching portion of the shuttle is returned and the held thread loop again transferred to the catching portion at the time of the next operation, and released by the return movement of the shuttle. This construction requires a shuttle which is entirely different from the shuttle used for permanent stitches. Furthermore, the thread loop must be twice transferred which causes operational difliculties and imperfect loop stitches.

Summary of the invention It is the main object of the invention to improve loop stitching made by sewing machines, and provide a simple and inexpensive shuttle arrangement for making loop stitches.

With this object in view, the present invention uses a rotary hook shuttle, and provides anchoring guide means for holding the thread loop formed by the rotary hook, and for smoothly releasing the loop. The anchoring guide means are preferably provided on a loop stitch shuttle which is secured to the rotary hook for rotation with the same. The present invention is also concerned with effectively carrying out the increase and reduction of the amount of thread supplied for loop stitches. The anchoring guide means are constructed and arranged so that the period for holding the loop of the needle thread on the rotary hook starts at the time of the catching of the thread by the rotary hook, includes the rising of the needle to the upper dead center position and the descent of the needle eye to a position cooperating with the rotary hook, and ending at the time when the needle eye is inserted into the preceding loop.

This operation requires an angle of rotation of more than 280 of the main shaft, corresponding to an angle of rotation of 560 for the rotary shuttles which rotate at twice the rotary speed of the main shaft. It is not possible for shuttles according to the prior art to hold the thread loop for more than 1 revolution, so that a rotary loop stitch shuttle is required in addition to the rotary hook shuttle. In accordance with the invention, the thread loop held by the loop stitch shuttle is expanded and reduced at the time desirable for loop stitch formation so that the loop stitches are smoothly formed.

Another object of the invention is to produce loop stitches by utilizing a standard rotary hook shuttle, which normally is used for permanent stitches. In accordance with the prior art, the shuttle itself must be exchanged, requiring special shuttles which are expensive to manufacture. In accordance with the present invention only a relatively small loop stitch shuttle is mounted on parts which are necessary for supporting a bobbin during the making of permanent stitches with upper and lower threads. The small loop stitch shuttle of the invention can be manufactured at low cost, and can be easily stored as a spare part or attachment for the machine. The machine can be easily adapted to loop stitching by attaching the loop stitch shuttle of the invention to the rotary hook shuttle.

Another object of the invention is to lightly tighten the loops in the material which are already released by the loop stitch shuttle. The tightening or fastening of stitches is generally carried out by the oscillatory thread guiding arm which takes the thread from tensioning means and supplies it to the needle. However, the fastening of loops by this arm causes frictional resistance of the thread in the needle hole of the needle plate, in the needle eye, and in the eye of the oscillatory thread guide arm. Particularly in loop stitching where the stitches are constructed of a single thread, the loop is fastened while sliding through the fabric or cloth so that the thread is subjected to higher frictional resistance than in permanent stitching.

In acordance with the invention, the fastening or tightening of the proceeding loop is carried out while the new loop caught by the rotary hook shuttle is held by the loop stitch shuttle, While the amount of needle thread supplied by the oscillatory thread guide arm is limited by a pin or thread guide. If necessary, the supply of the upper thread from the oscillatory thread guide arm is controlled by increasing the tension of the thread tensioning means so that the old loop is tightened after release by the shuttle. This reduces the stretch of the thread portion forming the preceding loop to a short distance so that a lightly tightened loop stitch is produced.

Another object of the invention is to supply different amounts of upper thread to the loop stitch shuttle, as compared with the amount supplied for the making of permanent stitches by a standard shuttle, which is due to the fact that thread requirements are different during loop stitching and permanent stitching with two threads. Insuflicient supply of upper thread may cause breakage of the thread, while excessive supply of thread will cause entwinement of the thread, repeated catching of the same thread loop, and the like. In order to overcome these disadvantages, the present invention provides a thread guide or control pin on the side of the oscillatory thread guide arm. The thread is guided from the tension regulating means over the thread supply control pin or guide, and to the eye of the needle. The cooperation between the thread supply control pin or thread guide, the loop stitch shuttle, and the oscillatory thread guide arm or take-up lever achieves a supply of upper thread corresponding to the length of thread required. The slackening of the upper thread is limited due to the mounting of the loop stitch shuttle in the rotary hook shuttle so that the loop stitch shuttle can be made very small.

Another object of the invention is to provide a loop stitch shuttle which can be easily manufactured. In accordance with the invention, the loop stitch shuttle is very small, and is mounted on a standard rotary hook shuttle Without any adaptations or changes. The small loop stitch shuttle can be made of sheet metal which is bent and soldered or welded to a cylindrical hub so that the loop stitch shuttle can be inexpensively manufactured.

Another object of the invention is to properly fasten and lightly tighten the loop stitches. In accordance with the invention, the thread of the respective preceding thread loop is used for expanding a newly formed thread loop. Especially after a needle eye has been placed in the cloth layer for constructing a new thread loop, it is almost impossible to supply thread through the fabric to the preceding loop since the thread passes in several bends through the cloth. In the present invention, the thread loop is transferred to the loop stitch shuttle so as to cause no substantial change in the required amount of upper thread especially at the stage in which the needle has penetrated the cloth for forming a new thread loop. This permits to accomplish loop stitching in properly slightly tightened condition.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Brief description of the drawing FIG. 1 is a front view illustrating a sewing machine provided with a loop stitch shuttle according to the invention;

FIG. 2 is a side view of the loop stitch shuttle according to a preferred embodiment;

FIG. 3 is a side view of the loop stitch shuttle of FIG. 2 as viewed from the other side;

FIG. 4 is a perspective view of the loop stitch shuttle;

FIG. 5 is a diagram illustrating the amount of upper thread supplied to the shuttle, the amount of upper thread required by the shuttle, the amount of upper thread required when the loop stitch shuttle according to the invention is attached to the rotary hook, and the amount of upper thread required in the event that a control pin or thread guide is used in combination with the loop stitch shuttle;

, FIG. 6 includes fourteen views, FIGS. 6A to FIG. 6N, which are front views illustrating successive positions of 4 of a base plate 17 which extends diametrically to hub portion 16 which is secured to shaft 7 in a predetermined angular position of base plate 17 by a screw 23. Base plate 17 ends at one end in a transversely projecting engaging portion 12 which is also connected with one end of the curved slanted guide member 9 which has an upper edge 9' and a lower edge 9". The upper edge of base plate 17 is formed with a pressing projection 11. The ends of guide member 10 are curved toward hub portion 16, and guide member 10 has anchoring portions 18 and 19 projecting in axial direction, guide portion 19 merging with the edge of base plate 17.

The end portion of the slanted guide member 9 is adapted to project into the rotary hook 1 beyond the front edge 21 so as to project into the slot into which the needle passes to permit catching of the thread by the catching portion 4 of rotary hook 1. The edge 9" receives and guides the thread portion R coming from the cloth and being guided by the front edge 21 of the rotary hook 1 while the thread loop is expanded. The other edge 9' of guide member 9 guides the needle thread drawn through the needle eye by catching portion 4 during the rotation of book 1. The slanted guide member 10 is inclined away from front edge 21 of rotary hook 1 so that only anchoring portion 18 projects into the rotary hook 1 beyond the front edge 21. Guide member 10 first receives thread drawn by catching portions 4 of rotary hook I so as to anchor the thread on the surface of the guide member 10 and on anchoring portion 18. Front edge 10' of guide member 10 receives needle thread pushed toward base portion 17 by front edge 9 during continued rotation, and pushes the thread further forward.

Front edges 9 and 10' of the guide members 9 and 10 form continuations of the same helix or spiral so that thread loops received by the same are subsequently pushed forward without slipping off irrespective of the high rotary speed of the rotary hook and the loop stitch shuttle, until released by pressing projection 11 at the end of the helical edge 10, as will be explained hereinafter.

As shown in FIG. 6A, base plate 17 extends substantially at right angles to a radius passing through the the needle, rotary hook, and loop stitch shuttle during 7 the formation of a loop stitch; and

FIG. 7 is a sectional view illustrating cloth with a row of loop stitches.

Description of preferred embodiments Referring to FIG. 1, a sewing machine has a spool supporting pin 54. The thread T is guided from the spool through a thread guide and passes through a conventional tensioning device 56 from where the thread passes through a thread guide 59 and the eye of an oscillatory thread guiding arm 57, another thread guide, and the eye of the needle 2. A rotary hook 1 has a thread catching portion 4, see also FIG. 6. A bobbin may be mounted in the rotary hook 1 to supply a shuttle thread which is connected with the needle thread to form stitches. Rotary hook 1 is mounted for rotation in an outer shuttle race 52 whose removable cover is held in position by arms 53.

As best seen in FIGS. 2 to 4, a loop stitch shuttle 6 has a hub portion with a central bore receiving drive shaft 7 and serves the purpose of anchoring thread loops caught in cooperation with the loop catching portion 4, and more particularly for holding a thread loop after it has been released by the catching portion 4.

Loop stitch shuttle 6 has two substantially spiral shaped guide members 9 and 10 which serve for expanding or contracting thread loops and project from opposite sides axis of rotation and a catching portion 4 of the rotary hook 1. Guide member 9 is located in the region of catching portion 4, and guide member 10 is positioned on the side of base plate 17 remote from catching portion 4. The relative positions are determined by placing hub portion 16 in proper angular relationship with shaft 7, and then securing hub portion 16 to shaft 7 by screw 23, see FIG. 3.

In a modification, loop stitch shuttle 6 is combined with rotary hook I and exchangeably mounted on the shaft. It is also possible to provide another anchoring portion at the lower end of hub 16 and to engage such anchoring portion with a projecting portion provided on the inner face of rotary hook I so as to position the rotary hook in a selected angular position relative to the loop stitch shuttle.

As shown in FIG. 1, thread guide 59 is located between the oscillatory thread guiding arm 57 and the tensioning means 56. In loop stitching operations accord ing to the invention, the thread is guided from the tensioning means 56 through thread guide 59 to the oscillatory arm 57. In this manner, the amount of thread delivered by the oscillatory arm 59 is influenced.

During loop stitching, the thread tension produced by tensioning means 56 is differently adjusted as compared with regular stitching during sewing operations. For example, if the tension of the needle thread is 40 grams during regular sewing operations with permanent stitching, the tensioning means 56 is set to produce a thread tension of between and 200 grams during the formation of loop stitching in accordance with the invention. Consequently, a standard sewing machine can be used for making regular permanent stitches, or loop stitches which can be easily opened and serve for temporarily connecting two layers of cloth.

The regulation of the tension of the needle thread during loop stitching is not necessarily obtained by adjustment of tensioning means 56, but it is also possible to mount the thread guide 59 on another reciprocating arm moving relative to arm 57 and consequently influencing the tension of the needle thread.

FIG. 5 has an ordinate representing the movement of the oscillatory thread guide arm 57 from its upper dead center position, and an abscissa representing the angle of rotation of the main shaft. The graph a--a represents the amount of needle thread required by the rotary hook for the stitches, and graph bb represents the amount of thread delivered by oscillatory thread guiding arm 57.

At an angle of revolution of about 210 of the main shaft, the thread loop is caught, and after that, the required amount of thread corresponds to graph aaa. At an angle of revolution of about 320, the thread loop is engaged by the loop stitch shuttle and then released by the catching portion 4, as will be explained with reference to FIG. 6C. The thread loop is held while the main shaft completes its first revolution and turns 220 of the next following revolution, so that the amount of thread required by the shuttle is represented by the graph portion a-a.

The amount of needle thread originally supplied by the oscillatory thread guide arm 57 is represented by the graph b-b-b, the dead center position of the thread guide arm 57 being reached when the shaft has substantially turned 290. Due to the provision of the thread guide 59, the amount of needle thread supplied in the lower dead center position of thread guide arm 57 is reduced between the angular positions 170 to 360 of the main shaft, so that the supplied thread is represented by the graph portion b'b instead of by the peak of graph bb--b.

Where graph portions bb or b'--b' are located below graph portions aa or zz'a', the relation between supplied needle thread and needle thread required by the shuttle is such that the needle thread becomes slack since more needle thread is supplied than is taken up by the shuttle. On the other hand, Where graph portions b--b or b are located above graph portions a--a or a'a, the amount of needle thread supplied by thread guide arm 57 to the shuttle is insufiicient. The actual amount of needle thread supplied by thread guide arm 57 is represented by the graph bbb-b, while at the same time the amount of thread required by the shuttle is represented by the graph aaa'--a' representing the action of the loop stitch shuttle according to the invention. The graph portions shown by chain lines are areas where the thread is tensioned by the shuttle. The curved graph portions forming points in the region of the angle of revolution of 210, represent the moment in which the thread loop is caught by the rotary hook.

FIG. 6 has fourteen views FIG. 6A to FIG. 6N representing successive operational positions of the shuttle and needle during loop stitching. The degrees of annular turning of the main shaft are indicated in each view so that the views can be respectively associated with corresponding portions or" the graphs of FIG. 5. In FIG. 6A, at an angle of the main shaft of 230 in relation to an initial position, the needle loop has just been caught by catching portion 4 of the rotary hook 1, which happened at an angle of 210, as represented by a pointed portion of graph a in FIG. 5. Catching portion 4 engages thread loop R on one side of needle 2 which has begun to move upward. FIG. 6B at 260 shows the rotary hook further turned and loop R expanded, while the guiding members 9 and 10 of the loop stitch shuttle are still inoperative. After the main shaft has turned 320 to the position shown in FIG. 6C, loop -R is further expanded and the front portion R of loop R slides along the front edge 21 of the rotary hook 1. Guide member 9 of the loop stitch shuttle 6 has no effect on the thread, but anchoring portion 18 of guide member 10 projects into the rotary hook '1 and catches the front loop portion R just before the position of FIG. 6C is assumed so that the thread loop R is expanded transversely and loop portion R is bent to an angular shape so that loop portion R and R are no longer parallel as in the position of FIG. 6B. As the rotation proceeds, loop R is no longer held by catching portion 4 of the rotary hook 1 so that loop portion R slides on the back of the rotary hook 1. This is made possible in a known manner by the provision of a coupling between a drive shaft and the rotary hook permitting the passage of the back portion of the loop. The drive shaft has slanted or eccentric coupling portions projecting into openings 25 and 26 of the rotary hook and moving in the same to form gaps through which the thread can slip. This construction is described in the copending application Serial No. 569,547 filed by Nakajima et al. on July 18, 1966, which discloses a shuttle construction, improved by the present invention for the purpose of making loop stitches.

Although the thread loop R is released by the catching portion 4 of rotary hook 1 between the positions shown in FIGS. 6C and 6D, it does not come off since front loop portion R is held by the anchoring portion 18 of guide member 10. When the main shaft has turned 20 of the second revolution, and after the needle has passed its upper dead center position at 360, the back loop portion R slips from the back of the rotary hook I to the front of the same and is located on the front edge 21 of the rotary hook I engaging anchoring portion 19 of guide member 10 so that the loop has a triangular shape.

As shown by graph portion aa' in FIG. 5, between the angular positions 320 and 20, the thread loop R is not slackened when catching portion 4 of the rotary hook I releases the loop. However, directly thereafter, a lesser amount of needle thread is required at the moment when back loop portion R moves to the front surface of rotary hook 1 approximately at the angular position 340. After that, and as shown by the graph portion a'a', approximately the same amount of needle thread is held by the loop stitch shuttle 6 between the anchoring portions 18 and 19 which hold a loop portion substantially parallel to the needle plate of the machine. During subsequent rotation of rotary hook 1 and loop stitch shuttle 6, the positions of the anchoring portions vary and the shape of the loop is changed, but since the anchoring portions 18, 19 are located opposite each other at substantial equal distances from shaft 7, rising of one anchoring portion, which causes a reduction of the amount of needle thread required for the loop, is compensated by the descent of the other anchoring portion. While the amount of needle thread forming the loop remains substantially the same, the shape and position of the loop is continuously changed due to the revolution of the loop stitch shuttle 6.

At an angle of 70 of the main shaft, in the position of FIG. 6E, the thread R which passes through the cloth and forms the front loop portion R is engaged by the slanted edge 9 of the slanted guide member 9 and advanced into the rotary hook 1 from the front edge 21, as shown in FIG. 3, and due to the helical shape of edge 9', the cloth thread R is pushed into contact with the front edge 21 of the rotary hook.

FIG. 6F at shows the position in which the cloth thread R' has been pushed forward by the slanted end portion of guide member 9. Base plate 17 is substantially parallel to the needle plate of the machine table so that cloth thread R' and needle thread R' are spread apart at a maximum angle. In this position, needle 2 is about to move downwardly into the expanded loop R.

FIG. 6G shows the position at an angle of rotation of the main shaft of 160. Base plate 17 of loop stitch shuttle 6 has turned more than 90 since the loop stitch shuttle 6 rotates at twice the speed of the main shaft, which has turned 50. In this position, base plate 17 is located substantially in a vertical plane passing through needle 2. Cloth thread R is pushed forward sufficiently by front edge 9' of guide member 9 to be transferred to the other guide member 10 while being continuously pushed forward by the spiral shape or helical slant of front edge 10" of guide member 10 so that cloth thread R, is now positioned in the region of pressing projection 11 of base plate 17, but not yet engaged by the same.

FIG. 6H shows the position at an angle of 210 in which needle 2 is again rising. Engaging portion 12 and pressing projection 11 of base plate 17 which curve toward guide member 10, hold the thread loop so that the same cannot slip off the loop stitch shuttle.

Turning through a small angle to the position of 225 shown in FIG. 61, brings the catching portion 4 of the rotary hook I to a position catching the needle thread so that a new thread loop R is formed by the rising needle 2. When the new thread loop R is caught, the old thread loop R formed of loop portions R and R' is sufficiently expanded and tensioned, as is apparent from FIGS. 6H and 61, so that the old loop R is not caught by catching portion 4 which engages the needle thread to form the new loop.

FIG. 6] shows the position after the main shaft has further turned 5, and the shuttle Base plate 17 of loop stitch shuttle 6 is slanted substantially at an angle of 45 or more relative to the needle plate so that thread loop R slips off pressing projection 11, which is best seen in FIGS. 2 to 4. As shown in FIG. 5, after the main shaft has turned 230 of its second revolution, the new thread loop R which was caught at 225, as represented by pointed portion of graph a, has been expanded by catching portion 4. No thread has been supplied to the oscillating guide arm 57 so that the old loop R is reduced.

As the revolution of the main shaft proceeds to 260, the position of FIG. 6K is assumed by the shuttle in which the new loop R is expanded by the rotary hook 1 while the old loop R is further reduced and tightened and completely separated from the loop stitch shuttle 6. As the new loop is being expanded, it takes thread from the old loop which is tightened.

FIG. 6L shows the engagement of the forward loop portion by guide member 9 of the loop stitch shuttle 6, corresponding to the position shown in FIG. 6C in which the front loop portion is held by guide member 10 since the shuttle has turned only 180 during the turning of the main shaft of 360.

At of the third revolution of the main shaft, the position of FIG. 6M is assumed by the shuttle in which the front loop portion R is spread between pressing projection 11 and anchoring portion 18 of guide member 9, whereupon in the position of FIG. 6N the loop is further transformed, while the old loop R is fully tightened in the stitched cloth. The upper dead center position of needle 2 is generally phase shifted relative to the upper dead center position of the oscillatory thread guide arm 57 an angle which corresponds to a 70 rotation of the main shaft. Due to this fact, the final fastening and tightening of the stitch is accomplished by the operation of the oscillatory thread guide arm 57.

When the new thread loop R is caught in the position of FIG; 61, and expanded between the positions of FIGS. 6] and 6K the operation is similar to the operation described with reference to FIGS. 6A and 6B. Accordingly, while the new loop proceeds through the stages shown in FIGS. 6L, 6M, and 6N, it is formed, maintained and changed as described with reference to FIGS. 6C, 6D, and 6E to accomplish the formation of a loop stitch relative to the displacement of cloth which is fed by conventional feeding means, whereupon the formation of desired loop stitches as shown in FIG. 6F and following views takes place.

The construction and operation of the present invention completely prevents the skipping of stitches. A skipped stitch has quite a different effect in loop stitching than in permanent stitching. While in permanent stitching, a skipped stitch is faulty, a skipped stitch must be completely prevented in a row of loop stitches, since the entire seam would open.

In accordance with the present invention, thread loop R, while anchored on the loop stitch shuttle 6, is fully expanded by the base plate 7 so as to cause the cloth thread R and the needle thread R' to make a sufficiently wide angle for permitting downward movement of needle 2, as shown in FIG. 6F. The descending needle moves completely between the spread threads R' and R and cannot produce a skipped stitch.

As regards the tightening of the old loops R after release of the same by the loop stitch shuttle 6 in the position shown in FIG. 61, stitches are formed while the cloth k is fed in the direction of the arrow P, as shown in FIG. 7. When the cloth thread R' is tensioned during the expansion of the loop R of the rotary hook 1, the thread is drawn in a direction of the arrows P to P to tighten the holding portion R of the loop stitch S This indicates that in the positions shown in FIGS. 6L, 6M, and 6N, the old loop R although loosened and removed from the loop stitch shuttle 6, can hold the loosened holding thread portion R of stitch S while the stitches S are being made, and thereafter. However, old stitches S S tend to be excessively tightened if an insufficient amount of thread is supplied while the preceding stitches S S are being made.

Accordingly, as mentioned above with reference to graph aa of FIG. 5, when the thread loop is transferred to the loop stitch shuttle, the required amount of upper thread is maintained so that the amount of upper needle thread required is not increased until the thread loop is released by he shuttle. Particularly before the position shown in FIG. 7, and before the needle eye 22 of needle 2 passes through the cloth k, the possible increase of the amount of needle thread required by the loop stitch shuttle 6 may be satisfactorily compensated by thread which has passed only once through cloth k. However, after the needle eye 22 has moved through the cloth to the position shown in FIG. 7, thread R' held by the loop stitch shuttle is held in the cloth after being bent three times. Due to the high frictional resistance against sliding of the thread, no thread can be supplied in the direction of the arrow P.

Accordingly, an increased amount of needle thread required for the loop stitch shuttle 6 would undesirably tighten stitches S S In conrtast, in the present invention, the amount of needle thread required by the shuttle 6 remains substantially the same in the angular positions 340, 360, 220, and needle 2 substantially completes the steps shown in FIGS. 6F, 6G, 6H, and 61 resulting in properly fastened loop stitches.

In the above-described embodiment, the loop stitch shuttle 6 is detachable from the shaft 7 of the bobbin so that one rotary hook can be used for permanent stitches and for loop stitches. However, if the rotary hook is used only for loop stitching, loop stitch shuttle '6 can be permanently combined with rotary hook 1. In such a construction, base plate 17 and guide members 9 and 10 are portions of the rotary hook. Since the guide members can be constructed without consideration regarding a standard rotary hook, the shape of the guide portions may be modified. In such a modified construction, only the rotary hook with the guide members has to be exchanged for standard rotary hook when permanent stitching is desired, instead of the exchange of the loop stitch shuttle 6 in the above-described preferred embodiment of the invention.

The thread guide 59 adjacent the thread guide arm 57 may be omitted. In this event, the oscillatory thread guide arm 57, draws amounts of thread similar to the representation of the graph bb-b in FIG. 5. This requires an eX- tension of the time for releasing the thread loop by the loop stitch shuttle 6 from 220 to 330 rotation of the main shaft, as shown in dash and dot lines c in FIG. 5. In this position, the amount of needle thread required by the rotary hook is a maximum. On the other hand, the amount of thread supplied by the oscillatory thread guide arm 57 is gradually reduced from its maximum as required for the tightening operation by which the old loop released by loop stitch shuttle 6 is tightened, the increased resist ance at the time of tightening being a mere inconvenience. The increase of the time during which the thread loop is held by the loop stitch shuttle 6 can be easily obtained by correspondingly designing the guide members 9 and 10 and the projections of the same.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of rotary hook shuttles difiering from the types described above.

While the invention has been illustrated and described as embodied in a loop stitching shuttle, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characeristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. In a sewing machine having a reciprocating needle, in combination, a loop stitch shuttle arrangement comprising a rotary hook means for catching a needle thread, forming a loop of the same, and releasing the loop in successive angular positions, said rotary hook means having a bobbin mounting means; and a loop stitch shuttle detachably connected to said bobbin mounting means for engaging the formed loop, said loop stitch shuttle including anchoring guide means rotatable therewith and having successive angular positions for anchoring and holding the released loop in spread condition during rotation of said rotary hook means and movement of said needle into said anchored loop, and for releasing said loop when said rotary hook means again catches the needle thread to form a new loop.

2. A loop stitch shuttle arrangement as claimed in claim 1, wherein said anchoring guide means is symmetrically spiral-shaped and has anchoring portions for anchoring the needle thread and guide portions for guiding said loop to a position releasing the same.

3. A loop stitch shuttle arrangement as claimed in claim 1, wherein said loop stitch shuttle has a portion detachably and angularly adjustably secured to said rotary hook means.

4. A loop stitch shuttle arrangement as claimed in claim 3, wherein said rotary hook means includes a shaft for mounting a bobbin; wherein said portion of said loop stitch shuttle is a hub portion detachably secured to said shaft; and wherein said anchoring guide means are secured to said hub portion.

5. In a sewing machine having a reciprocating needle, in combination, a loop stitch shuttle arrangement comprising a rotary hook means for catching a needle thread, forming a loop of the same, and releasing the loop in successive angular positions, said rotary hook means having a bobbin mounting means; and a loop stitch shuttle detachably connected to said bobbin mounting means for rotation therewith, and including anchoring guide means composed of a base plate and a pair of slanted spiral shaped guide members projecting from the ends of said base plate and located on opposite sides of the same "and having during rotation of said loop stitch shuttle successive angular positions for anchoring the released loop during rotation of said hook means and movement of said needle into said anchored loop, and for releasing said loop when said rotary hook means again catches the needle thread to form a new loop.

6. A loop stitch shuttle arrangement as claimed in claim 5, wherein one of said guide members has anchoring portions at the ends thereof, and wherein said base plate has a pressing projection at one end adjacent said one guide member, and an engaging portion at the other end adjacent one end of the other guide member.

7. A loop stitch shuttle arrangement as claimed in claim 6, wherein said other guide member has an end portion projecting into said rotary hook means, said rotary hook means having a catching portion located between said end portion and said one guide member.

8. A loop stitch shuttle arrangement as claimed in claim 7, wherein said guide members have spiral shaped edges located along a helical line.

9. A loop stitch shuttle arrangement as claimed in claim 5, wherein said rotary hook means has a thread catching portion; and wherein said base plate extends at right angles to a radial line from the axis of rotation of said rotary hook means to said catching portion.

10. A loop stitch shuttle arrangement as claimed in claim 5 comprising an oscillatory thread guide arm for supplying thread to said needle, tensioning means for tensioning the thread, and a thread guide adjacent said thread guide arm in the highest position of the same and guiding thread from said tensioning means to said thread guide arm.

11. A loop stitch shuttle arrangement as claimed in claim 5, wherein one of said guides includes anchoring portions for the thread spaced substantially the same distance from the axis of rotation of said rotary hook means.

12. A loop stitch shuttle arrangement as claimed in claim 1, wherein said anchoring guide means include a central portion mounted on said hook means, a base plate on said central portion extending diametrically to the same, a pair of thin curved guide members having edges located along a helical line, portions for anchoring the thread loop, and other portions for pushing the thread loop ofi said guide members in a predetermined angular position of said anchoring guide means and of said rotary hook means in relation to said needle.

13. In a sewing machine having a reciprocating needle, in combination, a loop stitch shuttle arrangement comprising a rotary hook means for catching a needle thread, forming a loop of the same, and releasing the loop in successive angular positions, said rotary hook means having a bobbin mounting means; and a loop stitch shuttle detachably connected to said bobbin receiving means for rotation therewith about an axis of rotation, and including two arcuate guide members disposed on opposite sides of said axis and having guide edges located along a helical line, one of said guide members having two spaced axially projecting anchoring portions for anchoring said loop during rotation of said hook means and loop stitch shuttle, and for releasing said loop when said hook means again catches the needle thread to form a new loop.

References Cited UNITED STATES PATENTS 33,439 10/ 1861 Marble 112201 1,570,667 1/1926 Grieb 112201 2,860,591 11/1958 Van Ness 1l2201 3,028,823 4/1962 O-ocho 112-201 X HERBERT F. ROSS, Primary Examiner. 

